Blister packs are of course well known for the storage and dispensing of pills, tablets and capsules, which are stored individually in cavities in a multi-cavity tray and removed by pushing each pill, tablet or capsule through a rupturable film or foil covering the cavities. The film or foil cover may be paper or a plastics film that can be peeled or torn away to expose the medication in the tray cavities, but is generally aluminum foil, which has the dual advantage of being easily rupturable and vapour-impermeable. Such blister packs normally carry only one unit dose of the same medication in each cavity.
Mixed medication blister packs have been proposed, having larger cavities for filling by a pharmacist, wherein each cavity in a multi-cavity tray can be filled with a mixture of medications. Typically, a tray may have a 2×7, 3×7, 4×7 or 5×7 array of cavities corresponding to 2, 3, 4 or 5 predefined medication times per day over a 7-day period, or one dose prescribed per day over a 2, 3, 4 or 5 week period. For example, a 4×7 tray may be filled with the medication to be taken at breakfast-time, lunchtime, early evening and immediately before retiring each day for a week, and then the filled cavities sealed with a rupturable or sequentially rupturable film or foil cover. Printed instructions on the pack identify the intended sequence of opening the individual cavities to dispense their contents according to the prescribed dosage regimen.
Disadvantages of conventional blister packs using a rupturable cover sheet are the difficulty experienced by some patients, particularly the elderly, in pushing the medication through the cover sheet, the need for expensive laminating equipment to seal the aluminum cover sheet over the cavities after the initial filling, and the difficulty experienced by the user in selecting the cavity containing the medication to be dispensed if the medication is pushed up through the foil from below. If the wrong cavity is opened by mistake then re-sealing is impossible because the cover sheet has ruptured.
A major disadvantage of the blister pack using a peelable cover sheet is the difficulty experienced by the user in peeling or tearing away a single selected portion of the cover sheet to expose the contents of only one preselected cavity. This can be achieved by scraping a finger-nail over a comer or tab portion of a segment of the cover sheet sealing the preselected cavity, but grasping that comer to peel away the complete segment sometimes requires considerable manual dexterity and possibly good eyesight, which is beyond the abilities of many elderly users. Also, if a tacky peelable adhesive is used to adhere the cover sheet to the tray, it is desirable to prevent the contents of the tray from coming into contact with the adhesive. Finally, the film cover sheet may not have as high a vapour impermeability as metal foil, so there is a reluctance on the part of pharmacists to pre-fill a mixed medication blister pack with medication for administration more than seven days in advance of the filling date, lest the medication deteriorates due to storage in humid ambient conditions.